A process and device for purifying electronic grade nitrous oxide from industrial waste gas

Abstract

The invention discloses a process and device for purifying electronic grade nitrous oxide from industrial waste gas, and specifically relates to the technical field of nitrous oxide production. The invention firstly adopts a water washing method to completely remove ammonia in the waste gas, and then removes the water vapor in the form of mist and ammonia dissolved in the water vapor mixed in the waste gas through a high-efficiency coalescer; the method of concentrating the nitrous oxide through an absorption tower and then purifying the nitrous oxide through low-temperature distillation avoids the possibility of nitrous oxide freezing in the low-temperature distillation system, is easier to operate, and produces less three wastes; ethanol is used as an absorbent, and the nitrous oxide of the raw gas is concentrated by an absorption method to ensure that the concentration of the nitrous oxide is greater than 60v%, and the concentrated gas is then removed by the low-temperature distillation system to remove light components and heavy component impurities, so that the top temperature of the low-temperature distillation tower can be controlled above the freezing point of the nitrous oxide, so that the problem of nitrous oxide freezing in the traditional low-temperature distillation system can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrous oxide production, and more specifically, to a process and a device for purifying electronic grade nitrous oxide from industrial waste gas. Background Art

[0002] Nitrous oxide is widely used in medicine, food, aerospace and other fields. With the rapid development of the information technology industry, N 2 As an important basic raw material in modern optoelectronics, microelectronics, large-scale integrated circuits and optical fiber manufacturing, the demand for O has increased accordingly and it is called the "food" of the IT industry.

[0003] Nitrous oxide is an important greenhouse gas that remains in the atmosphere for a long time and has a serious destructive effect on the ozone layer. Therefore, by recycling and reusing nitrous oxide, not only can greenhouse gas emissions be reduced, but also economic benefits can be obtained.

[0004] Industrial production emissions contain N 2 The main sources of tail gas are: gas mixtures generated in industrial processes such as the production of nitric acid and its related products, the production of adipic acid and its related products, and the caprolactam production process.

[0005] Patent CN201510654630.5 discloses a method for purifying N in tail gas. 2 O method, the raw gas is washed with acid to remove ammonia and washed with alkali to remove CO 2 and NO 2 , dust and water removal, compression cooling, adsorption purification, low temperature distillation to obtain N 2 O product.

[0006] Patent CN201780044589.7 discloses a method for purifying N2O in tail gas. The raw gas is separated by membrane to remove N 2 and O 2 To concentrate N 2 O, remove CO by adsorption 2 、NO 2 , water vapor and organic hydrocarbons, and then through the distillation process to obtain N 2 O product.

[0007] The impurity categories of the raw gas include most impurities, such as nitrogen, oxygen, ammonia, carbon monoxide, nitric oxide, water vapor, organic hydrocarbons, etc. The methods in the above two patent documents are not effective in removing the above impurities. Summary of the invention

[0008] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a process and an apparatus for purifying electronic grade nitrous oxide from industrial waste gas.

[0009] A process and device for purifying electronic grade nitrous oxide from industrial waste gas.

[0010] The specific purification process is as follows: petrochemical industry tail gas is used as raw material, first through the water washing system and coalescer system to remove ammonia and water in the tail gas; then after being pressurized by the absorption and pressurization system, it is sent to the absorption tower system to remove most of the N 2 and O 2 ; Finally, the light components remaining in the tail gas are removed by a cryogenic distillation system to obtain electronic grade nitrous oxide products;

[0011] The purification device specifically includes a raw gas blast pressurization system, a water washing system, a coalescer system, an absorption pressurization system, an absorption tower system, an absorbent recovery system, a cryogenic distillation pressurization system, a cryogenic distillation system, and a product storage system.

[0012] Furthermore, the process and apparatus for purifying electronic grade nitrous oxide from industrial waste gas specifically comprises the following steps:

[0013] (1) Raw gas blasting and pressurizing system: The raw gas is first sent to the water washing system after the liquid phase material is removed by the separator and then pressurized by the blower;

[0014] (2) Water washing system: The purpose of the water washing system is to remove ammonia. An ammonia washing tower and a washing water recovery tower are set up. The raw gas passes through the ammonia washing tower to remove ammonia in the raw gas, and then passes through the washing water recovery tower to obtain recycled water, which is recycled for use;

[0015] (3) Coalescer system: The purpose is to remove water and residual ammonia droplets in the raw gas; remove NH 3 After the waste gas is removed from the waste gas by the separator to remove free water, it is then removed from the waste gas by the high-efficiency coalescer to remove the mist-like water vapor and the ammonia dissolved in the water vapor.

[0016] (4) Absorption booster system: The gas coming out of the coalescer is pressurized by the absorption booster system to the pressure required by the absorption tower system;

[0017] (5) Absorption tower system: The absorption tower system uses an absorbent to absorb the nitrous oxide component of the raw gas;

[0018] (6) Absorbent recovery system: a desorption tower is used to desorb the gas absorbed by the absorbent, and the absorbent is recycled;

[0019] (7) Cryogenic distillation boosting system: The desorbed gas obtained from the absorbent recovery system is boosted by the cryogenic distillation boosting system and then sent to the cryogenic distillation system;

[0020] (8) Cryogenic distillation system: purifies the pressurized raw gas and removes light components and heavy components in the raw gas;

[0021] (9) Product storage system: storage of liquid product nitrous oxide.

[0022] Furthermore, the water washing system includes an ammonia washing tower and a washing water recovery tower, the washing water enters the ammonia washing tower from the top, the raw gas enters the ammonia washing tower from the bottom, the gas removed from the ammonia washing tower is obtained from the top of the ammonia washing tower, and is sent to the agglomerator system; the water absorbed by the ammonia at the bottom of the ammonia washing tower is sent to the washing water recovery tower, ammonia-containing wastewater is obtained from the top of the washing water recovery tower, and the recovered water obtained from the bottom is returned to the ammonia washing tower as washing water for recycling; the ammonia washing tower is an absorption tower, and the washing water recovery tower is a distillation tower, and the washing water recovery tower includes a top cooling system and a reflux system, and a bottom reboiler system; the water recovered at the bottom of the washing water recovery tower needs to be cooled to 30-40°C by a cooler before it can be returned to the ammonia washing tower system for reuse; the gas at the top of the washing water recovery tower is heat-exchanged with its feed and then goes to the separator.

[0023] Furthermore, the coalescer system includes a coalescer, which is provided with a pre-separator to separate free water, and then removes the droplets in the form of mist through the coalescer, thereby separating H 2 O and NH 3 The content was reduced to below 1ppm.

[0024] Furthermore, the absorption tower system includes an absorption tower, and the absorbent enters the absorption tower from the top, and the absorbent can dissolve N 2 O, but cannot dissolve N 2 and O 2 The N insoluble in the absorbent is obtained from the top of the absorption tower. 2 and O 2 , as waste gas sent out of the boundary area, the nitrogen-containing 2 The rich absorbent of O is sent to the absorbent recovery system; the absorbent used in the absorption tower is ethanol.

[0025] Furthermore, the absorbent recovery system includes a stripping tower in which the N absorbed by the absorbent is 2 O and a small amount of N 2 , O 2 All desorption is done at one time, and the absorbent obtained from the bottom of the stripping tower is returned to the absorption tower for recycling, and the desorbed gas obtained from the top of the stripping tower is sent to the low-temperature distillation and pressurization system; the stripping tower is a distillation tower, and the stripping tower system includes a top cooling system and a reflux system, as well as a bottom reboiler system; the absorbent recovered from the bottom of the stripping tower needs to be cooled to 30-40°C by a cooler and then returned to the absorption tower system for reuse.

[0026] Furthermore, the cryogenic distillation system may include a one-tower process or a two-tower process according to the composition of impurities in the raw gas; the cryogenic distillation system includes a cryogenic distillation tower, and the cryogenic distillation tower includes a tower top cooling system and a reflux system, and a tower bottom reboiler system.

[0027] Furthermore, the product storage system can use vacuum insulated low-temperature storage tanks or high-pressure normal-temperature steel cylinders for storage according to the product output.

[0028] Furthermore, the operating pressure of the ammonia washing tower is 0.2-0.4 MPaG, the number of theoretical plates is 8-20 plates; the operating pressure of the washing water recovery tower is 0.15-0.35 MPaG, the number of theoretical plates is 8-20 plates, the tower top temperature is 90-120°C, the tower bottom temperature is 110-140°C, and the reflux ratio is 2-4; the operating pressure of the absorption tower is 1.2-1.4 MPaG, the number of theoretical plates is 20-40 plates; the operating pressure of the desorption tower is 1.0-1.3 MPaG, the number of theoretical plates is 15-35 plates, the tower top temperature is -55--40°C, the tower bottom temperature is 140-160°C, and the reflux ratio is 2-4; the operating pressure of the cryogenic distillation tower is The pressure is 2.2-2.8MPaG, the number of theoretical plates is 15-30 plates, the top temperature is -80--90℃, the feed temperature is -20--40℃, the bottom temperature is -5--15℃, and the reflux ratio is 2-4; the pressure of the raw gas blast boosting system is increased to 0.2-0.4MPaG; the pressure of the absorption boosting system is increased to 1.2-1.4MPaG; the pressure of the low-temperature distillation boosting system is increased to 2.2-2.8MPaG; the storage pressure of the vacuum insulated low-temperature storage tank is 1.0-2.5MPaG, and the storage temperature is -15--35℃; the storage pressure of the high-pressure normal temperature cylinder is 6.0-7.0MPaG.

[0029] Furthermore, the operating pressure of the ammonia washing tower is 0.2-0.3 MPaG, the number of theoretical plates is 10-15 plates; the operating pressure of the washing water recovery tower is 0.15-0.25 MPaG, the number of theoretical plates is 10-15 plates, the top temperature is 90-120°C, the bottom temperature is 110-140°C, and the reflux ratio is 2-4; the operating pressure of the absorption tower is 1.2-1.3 MPaG, the number of theoretical plates is 25-30 plates; the operating pressure of the desorption tower is 1.0-1.1 MPaG, the number of theoretical plates is 20-25 plates, the top temperature is -55--40°C, the bottom temperature is 140-160°C, and the reflux ratio is 2-4. The flow ratio is 2 to 4; the operating pressure of the low-temperature distillation tower is 2.3 to 2.4 MPaG, the number of theoretical plates is 20 to 25 plates, the top temperature is -80 to -90°C, the feed temperature is -20 to -40°C, the bottom temperature is -5 to -15°C, and the reflux ratio is 2 to 4; the pressure of the raw gas blast booster system is 0.2 to 0.3 MPaG; the pressure of the absorption booster system is 1.2 to 1.3 MPaG; the pressure of the low-temperature distillation booster system is 2.3 to 2.5 MPaG; the product storage system adopts high-pressure normal temperature cylinders for storage, and the storage pressure of the high-pressure normal temperature cylinders is 6.0 to 7.0 MPaG.

[0030] Technical effects and advantages of the present invention:

[0031] 1. The present invention contains N 2 The industrial waste gas of O is first washed with water to completely remove NH 3 ; dissolved NH 3 The water is distilled to remove the NH 3 After recycling, NH 3 After the exhaust gas is removed from the waste gas by the separator to remove free water, it is then removed from the waste gas by the high-efficiency coalescer to remove the mist-like water vapor and the ammonia dissolved in the water vapor. 2 O and NH 3 The content of H 2 O and NH 3 The mixed gas first passes through the absorption tower to absorb the N 2 O, vs. N 2 After the O is concentrated, the absorbed N 2 O and a small amount of N 2 , O 2 Desorption, recycling of absorbent, N in desorbed gas 2 The concentration is greatly reduced, and after being pressurized, it is sent to a cryogenic distillation tower to remove light component impurities from the top of the tower, and finally 4N electronic grade N is obtained from the bottom of the tower. 2 O product;

[0032] 2. The method of the present invention concentrates nitrous oxide by an absorption tower and then purifies nitrous oxide by cryogenic distillation, thereby avoiding the possibility of nitrous oxide freezing in the cryogenic distillation system, making the operation easier and producing less three wastes; ethanol is used as an absorbent to enrich the nitrous oxide in the raw gas by absorption to ensure that the concentration of nitrous oxide is greater than 60v%, and the enriched gas is then passed through a cryogenic distillation system to remove light components and heavy component impurities, so that the top temperature of the cryogenic distillation tower can be controlled above the freezing point of nitrous oxide, thereby solving the problem of nitrous oxide freezing in the traditional cryogenic distillation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 It is an overall process diagram of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] like Figure 1 As shown:

[0037] The present invention provides a process and device for purifying electronic grade nitrous oxide from industrial waste gas. The purification device specifically comprises a raw gas blast pressurization system, a water washing system, a coalescer system, an absorption pressurization system, an absorption tower system, an absorbent recovery system, a cryogenic distillation pressurization system, a cryogenic distillation system, and a product storage system. The specific process steps are as follows:

[0038] (1) Raw gas blast pressurization system: The waste gas raw material is sent from the boundary area to the raw gas buffer tank, and the free water obtained at the bottom of the tank is sent to the waste water main. The gas at the top of the tank is pressurized to 0.22MpaG by the booster blower, cooled by the fan aftercooler, and then sent to the separator, and then to the bottom of the ammonia washing tower.

[0039] (2) Water washing system: The pressurized raw gas is sent to the bottom of the ammonia washing tower, and the washing water enters from the top of the ammonia washing tower. 3 After being absorbed by water, the gas is heated up by ammonia heat exchange from the bottom of the tower and then sent to the washing water recovery tower. The desorbed gas at the top of the washing water recovery tower enters the reflux tank of the washing water recovery tower after heat exchange and cooling. Part of the separated waste water returns to the tower as reflux, and the rest is used as a wastewater delivery device. The separated non-condensable gas is sent to the waste gas main pipe. The recovered water obtained at the bottom of the washing water recovery tower is cooled by the recovered water cooler and then returned to the washing ammonia tower for recycling.

[0040] (3) Coalescer system: The waste gas from the top of the ammonia scrubbing tower is sent to the coalescer after the free water is separated by the pre-separator. The coalescer can remove the droplets in the form of mist, thereby converting H 2 O and NH 3 The content was reduced to below 1ppm.

[0041] (4) Absorption and pressurization system: The gas coming out of the coalescer is pressurized to 1.22MPaG by the No. 1 compressor and then sent to the absorption tower.

[0042] (5) Absorption tower system: The gas pressurized by compressor No. 1 is sent to the bottom of the absorption tower, and the absorbent enters the absorption tower from the top. 2 O, but cannot dissolve N 2 and O 2 The ethanol is used as the absorbent, and the N insoluble in the absorbent is obtained from the top of the absorption tower.2 and O 2 , and the rich absorbent obtained from the bottom of the absorption tower is sent to the deabsorption tower as waste gas out of the boundary area.

[0043] (6) Absorbent recovery system: The N absorbed by the absorbent is recovered in the desorption tower. 2 O and a small amount of N 2 , O 2 All desorption is performed at one time. The absorbent obtained from the bottom of the stripping tower is cooled by the absorbent cooler and then returned to the absorption tower for recycling. The desorbed gas obtained from the top of the stripping tower is cooled by the stripping tower top cooler and then sent to the stripping tower reflux tank. The separated liquid is sent to the top of the stripping tower as reflux. The separated non-condensable gas is heated by the non-condensable gas heat exchanger in the stripping tower and then sent to the 2# compressor.

[0044] (7) Cryogenic distillation pressurization system: The non-condensable gas obtained from the top of the stripping tower is pressurized to 2.5 MPaG by the 2# compressor. The pressurized gas is heat exchanged with the inlet gas of the 2# compressor and cooled down, and then sent to the cryogenic distillation tower heat exchanger for further cooling. It is then sent to the cryogenic distillation tower feed cooler for further cooling to -30°C before being sent to the cryogenic distillation tower.

[0045] (8) Cryogenic distillation system: There are no heavy impurities in this embodiment, so the cryogenic distillation system only has one distillation tower to remove light impurities in the feed gas. The purpose of the cryogenic distillation tower in this embodiment is to remove N 2 The light component N in O 2 and O 2 The key to operation is to control the condensation temperature inside the tower and at the top of the tower at N 2 Above the freezing point of O, avoid N 2 O freezes. The gas obtained from the top of the cryogenic distillation tower is cooled to -85°C by the cryogenic distillation tower top cooler, and the non-condensable gas is sent to the cryogenic distillation tower heat exchanger for heating and then sent to the exhaust gas main pipe, and the condensate is returned to the top of the cryogenic distillation tower as reflux. 2 OThe product is pumped to the product storage system.

[0046] (9) Product storage system: In this embodiment, nitrous oxide is stored in high-pressure steel cylinders.

[0047] The above process scheme, the above implementation case, and the logistics data of the main logistics are shown in Tables 1 and 2.

[0048] Table 1 Logistics data table (I)

[0049]

[0050] Table 2 Logistics data table (II)

[0051]

[0052]

[0053] The present invention provides a method for purifying 4N electronic grade nitrous oxide (N 2 O) method, and an apparatus system for implementing the method; containing N 2 The industrial waste gas of O is first washed with water to completely remove NH 3 ; dissolved NH 3 The water is distilled to remove the NH 3 After recycling, NH 3 After the exhaust gas is removed from the waste gas by the separator to remove free water, it is then removed from the waste gas by the high-efficiency coalescer to remove the mist-like water vapor and the ammonia dissolved in the water vapor. 2 O and NH 3 The content of H is controlled below 1ppm. 2 O and NH 3 The mixed gas first passes through the absorption tower to absorb the N 2 O, vs. N 2 After the O is concentrated, the absorbed N 2 O and a small amount of N 2 , O 2 Desorption, recycling of absorbent, N in desorbed gas 2 The concentration is greatly reduced, and after being pressurized, it is sent to a cryogenic distillation tower to remove light component impurities from the top of the tower, and finally 4N electronic grade N is obtained from the bottom of the tower. 2 Compared with the prior art, the present invention proposes a method of concentrating N 2 O, and then purify N by low temperature distillation 2 O method, avoiding the cryogenic distillation system N 2 O possibility of freezing, easier operation, less waste;

[0054] The method of the present invention uses an absorption tower to concentrate nitrous oxide and then uses cryogenic distillation to purify the nitrous oxide, thereby avoiding the possibility of nitrous oxide freezing in a cryogenic distillation system, making the operation easier and producing less three wastes; ethanol is used as an absorbent to enrich the nitrous oxide in raw gas by absorption to ensure that the concentration of the nitrous oxide is greater than 60% by volume; the enriched gas is then passed through a cryogenic distillation system to remove light components and heavy component impurities, so that the tower top temperature of the cryogenic distillation tower can be controlled above the freezing point of the nitrous oxide, thereby solving the problem of nitrous oxide freezing in a traditional cryogenic distillation system.

[0055] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for purifying electronic grade nitrous oxide from industrial waste gas, characterized in that: The specific steps include: (1) Raw gas blasting and pressurizing system: The raw gas is firstly sent to the water washing system after the liquid phase material is removed by the first separator and then pressurized by the blower; (2) Water washing system: an ammonia washing tower and a washing water recovery tower are set up. The raw gas passes through the ammonia washing tower to remove ammonia in the raw gas, and then passes through the washing water recovery tower to obtain recycled water, which is recycled for use; (3) Coalescer system: After the NH3 is removed, the waste gas passes through the second separator to remove free water, and then passes through the coalescer to remove the mist-like water vapor and ammonia dissolved in the water vapor mixed in the waste gas; (4) Absorption booster system: The gas coming out of the coalescer is pressurized by the absorption booster system to the pressure required by the absorption tower system; (5) Absorption tower system: The absorption tower system uses an absorbent to absorb the nitrous oxide component of the raw gas, and the absorbent is ethanol; (6) Absorbent recovery system: a desorption tower is used to desorb the gas absorbed by the absorbent, and the absorbent is recycled; (7) Cryogenic distillation boosting system: The desorbed gas obtained from the absorbent recovery system is boosted by the cryogenic distillation boosting system and then sent to the cryogenic distillation system; (8) Cryogenic distillation system: purifies the pressurized raw gas and removes light components and heavy components in the raw gas; (9) Product storage system: for storing liquid product nitrous oxide; the operating pressure of the ammonia washing tower is 0.2-0.4 MPaG, and the theoretical number of plates is 8-20 plates; the operating pressure of the washing water recovery tower is 0.15-0.35 MPaG, and the theoretical number of plates is 8-20 plates, the tower top temperature is 90-120°C, the tower bottom temperature is 110-140°C, and the reflux ratio is 2-4; the operating pressure of the absorption tower is 1.2-1.4 MPaG, and the theoretical number of plates is 20-40 plates; the operating pressure of the desorption tower is 1.0-1.3 MPaG, and the theoretical number of plates is 15-35 plates, and the tower The top temperature is -55 to -40°C, the bottom temperature is 140 to 160°C, and the reflux ratio is 2 to 4; the operating pressure of the low-temperature distillation tower is 2.2 to 2.8 MPaG, the number of theoretical plates is 15 to 30 plates, the top temperature is -80 to -90°C, the feed temperature is -20 to -40°C, the bottom temperature is -5 to -15°C, and the reflux ratio is 2 to 4; the pressure of the raw gas blast boosting system is increased to 0.2 to 0.4 MPaG; the pressure of the absorption boosting system is increased to 1.2 to 1.4 MPaG; the pressure of the low-temperature distillation boosting system is increased to 2.2 to 2.8 MPaG.

2. A process for purifying electronic grade nitrous oxide from industrial waste gas according to claim 1, characterized in that: The washing water enters the ammonia washing tower from the top, and the raw gas enters the ammonia washing tower from the bottom. The gas freed of ammonia is obtained from the top of the ammonia washing tower and sent to the coalescer system; the water absorbed by ammonia at the bottom of the ammonia washing tower is sent to the washing water recovery tower, and ammonia-containing wastewater is obtained from the top of the washing water recovery tower. The recovered water obtained from the bottom is returned to the ammonia washing tower as washing water for recycling; the ammonia washing tower is an absorption tower, and the washing water recovery tower is a distillation tower. The washing water recovery tower includes a tower top cooling system, a reflux system, and a tower bottom reboiler system; the water recovered at the bottom of the washing water recovery tower is cooled to 30-40°C by a cooler and then returned to the ammonia washing tower for reuse.

3. A process for purifying electronic grade nitrous oxide from industrial waste gas according to claim 1, characterized in that: The product storage system adopts vacuum insulation low-temperature storage tanks or high-pressure normal temperature cylinders for storage.

4. A process for purifying electronic grade nitrous oxide from industrial waste gas according to claim 3, characterized in that: The storage pressure of the vacuum insulated low-temperature storage tank is 1.0~2.5MPaG, and the storage temperature is -15~-35℃; the storage pressure of the high-pressure normal temperature cylinder is 6.0~7.0MPaG.

5. A process for purifying electronic grade nitrous oxide from industrial waste gas according to claim 1, characterized in that: The operating pressure of the ammonia washing tower is 0.2-0.3 MPaG, and the number of theoretical plates is 10-15 plates; the operating pressure of the washing water recovery tower is 0.15-0.25 MPaG, the number of theoretical plates is 10-15 plates, the top temperature is 90-120°C, the bottom temperature is 110-140°C, and the reflux ratio is 2-4; the operating pressure of the absorption tower is 1.2-1.3 MPaG, and the number of theoretical plates is 25-30 plates; the operating pressure of the desorption .... The operating pressure is 1.0-1.1 MPaG, the number of theoretical plates is 20-25 plates, the top temperature is -55--40°C, the bottom temperature is 140-160°C, and the reflux ratio is 2-4; the operating pressure of the low-temperature distillation tower is 2.3-2.4 MPaG, the number of theoretical plates is 20-25 plates, the top temperature is -80--90°C, the feed temperature is -20--40°C, the bottom temperature is -5--15°C, and the reflux ratio is 2-4.

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